On the Look Out for Resistant Ryegrass

The first cases of resistant annual ryegrass from McLaren Vale were collected by myself and confirmed by Dr Angela Baker of the CRC-weeds based at the University of Adelaide in 2005. Since that time these ‘super weeds’ have been spreading and many cases remain undocumented and unnoticed.

Resistant annual ryegrass shows up where farmers have been applying glyphosate herbicides, commonly known as Roundup. This is particularly the case in vineyards and olive groves that were planted in old almond orchards.

When glyphosate first came onto the market in the 1960’s it was used heavily by almond growers with many sprays applied without rotation with another herbicide group. After frequent herbicide applications these grass populations evolved from being susceptible, to being resistant to the glyphosate herbicides. Once resistance was established the plants began to spread.

This vineyard has herbicide resistant annual ryegrass growing undervine.
Now when glyphosate is used on resistant ryegrass it is not controlled well and it multiplied becoming a weed. In many cases they keep growing and start to smother other plants.

These ‘super weeds’ first appear as a scattering of single plants or small patches of plants that survived after a glyphosate application.

If you have seen this problem on your farm last year, seek advice. It is important to stop this ryegrass from seeding and increasing next year. If you continue to use glyphosate you only make the problem worse. Increasing the rate of application does not help, as the ryegrass continues to thrive.

This is a serious problem for farmers and action needs to be taken to prevent these weeds from taking over large patches of the district.

The only solution is to used alternative control measures, like cultivation or knifing or by using other groups of herbicide, like Alliance (a combination of the Amitrole and Paraquat herbicides), or grass selective herbicides (Fulisade).

For more information contact me at DJ’s – 8323 8339.


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